Approaches to blind equalization of signals with multiple modulus

The constant modulus algorithm (CMA) and decision-directed (DD) equalizer are two ways to approach blind equalization of signals that are known to lie on a circle of fixed radius, but where specific values at any given time are unknown. In m-ary quadrature amplitude modulation, the signals lie on n circles of known radius. The authors present two possible approaches to the n-modulus problem, both in the spirit of feature reconstruction algorithms. The multiple-modulus algorithm uses a straightforward generalization of the CMA cost function to derive its update, whereas the decision-adjusted-modulus algorithm is a hybrid of the CMA and DD approaches